Alarm switching device for rotary elements



ALARM SWITCHING DEVICE FOR ROTARY ELEMENTS Filed May 25. 1951 INVENTOR. E. 5. Mc LAR/V BW y* ATTRNEY Patented Nov. E, 1955 tice ALARM swlrcnnso DEVICE non ROTARY ntntvinNrs Ernest S. McLarn, Manhasset, N. Y., assigner to International Standard Electric Corporation, New York, N. Y., a corporation of Delaware Application May 23, 1951, Serial No. 227,877

6 Claims. (Cl. 2G080) The present kinvention relates to alarm switching devices for rotating elements and more particularly to a device adapted to indicate automatically any loss in rotational speed of a driving shaft, such as might be used for the continuously rotating parts of automatic telephone systems.

'In certain well known automatic telephone systems, each bay or switch frame has a main vertical rotating shaft arranged to operate a plurality of selector switches in a manner known per se which forms no part of this invention. The satisfactory operation of this system depends to a very considerable extent upon the uniformity of the rotational speed of the vertical drive shaft. It has been found, therefore, in accordance with this invention, that it is highly desirable to incorporate in systems of this type sensitive and reliable means for automatically indicating immediately when the rotational speed of any shaft is reduced7 so that steps may be taken to correct this defective condition. It has also been found desirable to provide such warning means in such manner as not to interfere with the complex mechanical and electrical arrangements forming part of a selector switch frame in telephone systems of the type to which this invention relates.

The principal object of the invention therefore is to provide a simple and highly sensitive alarm switching device of the above-described nature which can be easily and economically installed for operation in connection with any rotating vertical shaft, such as those used in 1nown telephone switching systems.

Another object of the invention is to provide such an alarm switching device which will close an electrical circuit when the speed of the shaft falls below a predetermined value.

The above and other objects of the present invention are accomplished by providing a governor or rotary alarm switching device comprising a suitable weight carried by the rotating drive shaft which, during normal operational speed of the system, is forced away by centrifugal force from a fixed contact disc, but which will make contact with said disc automatically even upon a moderate deceleration of the rotational speed of the shaft, thus closing an electrical circuit and sounding an alarm or otherwise indicating an alarm warning.

rhe above and other features, objects and advantages of this invention will become more apparent from the following detailed description of a preferred embodiment thereof, taken in conjunction with the accompanying drawing whose single figure shows a side view of the alarm switching device of the invention as mounted at the top of the vertical drive shaft in each bay of a telephone selector system.

Referring now to the drawing, there is shown a. switch frame 1 and a yoke 2 iixedly connected to the frame and rotatably supporting the vertical drive shaft 3 in posi tion. The speed alarm switching control device is mounted on shaft 3 and is generally indicated by reference numeral 4. The device 4 may be provided with a dust-proof enclosure consisting of telescoping hollow cylindrical covers 5 and 6 having respective end walls 7 and d. The covers may be made of any suitable material and are preferably transparent. Cellulose acetate covers have been found satisfactory. The lower end wall 7 rests on a washer 9 which consists of a soft material such as felt or rubber, and is supported in turn upon the yoke 2.

The alarm switching device proper comprises a metal collar 16 and a metal weight 11 mounted on collar 10 by means of a metal supporting rod 12, and metal disc 13. The collar 10 is provided with a central bore adapted to accommodate the shaft 3 and also with a radial channel 14, adapted to receive a set screw 15. Shaft 3 is provided with a keyway 16 and the set screw is tightened into the keyway to fasten the collar to the shaft. As shown, the rod 12 is attached to collar 10 in a slightly inclined position, and may be screwed into the collar or may be connected thereto by any other suitable means. Weight 11 is cylindrical and is provided with a central bore of greater diameter than the diameter of rod 12, a ball bearing 17 being provided within the central bore between rod 12 and the wall of the bore in the weight to reduce operational friction. The weight is thus free to rotate and to slide axially on the rod 12. When the shaft rotates, the weight 11 will be forced by centrifugal force to glide on the ball bearing along rod 12 away from the shaft. End plate 18 is attached to rod 12 to stop the outward movement of the weight and hold the weight on the rod. The disc 13 is insulatedly supported from the frame 1 by means of a plate member 19 of insulating material which is shown fastened to the switch frame 1 by means of screws 20 and 21, but it is understood that any other suitable fastening means could be used. The disc 13 is attached to the plate 19 by a bolt 22 which extends through the plate and also through the wall 8 of the cover 6 and is secured by suitable nuts 23 and 24 above and below the plate and cover wall. A wire 24 is connected to the bolt 22 for making the electrical connection to an alarm device 2S which is connected in series with a battery 26 or other source of current to the frame 1.

The alarm switching device of this invention may be simply assembled and arranged at the top of a conventional switch frame or bay in the following manner:

The washer 9 is placed over the drive shaft 3 and the bottom 7 of the enclosure 5 is positioned over the washer, with the washer 9 and the end wall 7 in Contact with each other. The collar 10 having the weight 11 attached thereto is then placed over the shaft and the set screw 15 is tightened, so as to locate and fasten the collar on the shaft in its desired position. The plate 19 with the disc 13 and cover 6 attached thereto is placed in position and secured by the screws 20 and 21, the upper cover 6 being telescoped in the lower part of the cover 5. When properly assembled the disc 13 is coaxial with the shaft 3 and spaced from the end thereof.

In the operation of the device, when the vertical drive shaft rotates at the desired uniform speed, the weight 11 will be forced outwardly by centrifugal force away from the disc 13 to the limit of its movement and will remain in that position until the speed decreases. lf the rotational movement of the shaft is decreased for any reason, the weight 11 will slide inwardly upon its rod 12 under the influence of gravity and will thus contact disc 13, thereby completing the circuit through the alarm device 25 and operating the alarm.

As the weight 11 touches the edge of the disc it will commence to rotate because of the friction with the disc and will thus roll around the edge of the disc making a wiping contact therewith which will keep the edge clean and insure good contact. Preferably the disc 13 and the weight 11 should be plated with a tiash coat of silver to ensure of a reliable electrical contact.

While the invention has been described with reference to the single embodiment shown in the drawing, it is to be understood that the same has been given merely for the purpose of illustration and not as a limitation upon the spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. An alarm switching device comprising a fixed frame, a vertical rotatable shaft, a rod Xed to and extending away from said shaft at a fixed acute angle to a plane normal to the axis of said shaft, a pair of switch elements comprising a weight and a stationary member, means for mounting said weight slidably on said rod whereby said weight is forced outwardly along said rod and away from said shaft by centrifugal force as the shaft rotates at a given speed and said weight is moved inwardly along said rod and toward said shaft by gravity below said speed, said stationary member Xed to said frame and adapted to be contacted by said weight when said weight is moved in one direction,

2. An alarm device as defined in claim 1, wherein said means for mounting said weight comprises an opening in said weight through which said rod passes.

3. An alarm switching device, as defined in claim 1, in which said means for mounting the weight slidably on the rod includes means for also mounting the weight rotatably on the rod, and in which said stationary fixed member is a disc mounted perpendicular to the axis of the shaft and concentric therewith, said weight having a surface adapted to rotate around the edge of said disc when the weight is in Contact with said disc.

4. An alarm switching device comprising a xed frame, a shaft, means for mounting said shaft for rotation on a vertical axis, a rod obliquely attached to said shaft, ball bearing means slidably arranged on said rod, a pair of switch elements comprising a weight and a stationary member, said weight mounted on said ball bearing means, stop means at a predetermined location of the rod for halting said outward movement of the weight upon accell eration of the rotational velocity of the shaft, said stationary member arranged on said frame adjacent the shaft and the weight and adapted to be contacted by the weight upon radial inward movement of said weight.

5. An alarm switching device, as dened in claim 4, further comprising closure means surrounding said rod and weight.

6. An alarm device, as defined in claim 4, in which the weight is cylindrical in shape and the member is a disc mounted perpendicularly of said shaft and concentric therewith in such a position as to have its edge engaged by the inner end surface of said weight when said weight contacts said disc.

References Cited in the le of this patent UNITED STATES PATENTS 854,918 Weber May 28, 1907 925,312 Downer June 15, 1909 1,229,266 Hillhouse u June 12, 1917 1,680,944 Hoglund Aug. 14, 1928 2,543,877 Stein Mar. 6, 1951 

